Method of producing crack-free electron beam welds of jet engine components

ABSTRACT

Crack-free welds of jet engine components formed essentially of a heat resistant nickel-base alloy having a tendency to be weldcrack sensitive are produced by abutting selected surface of at least a pair of structural elements of said nickel-base alloy, the elements being assembled in welding relationship with an iron-base shim therebetween, the elements being electron beam welded together into a unitary structure by melting the iron-base shim at the interface of the abutting surfaces, whereby the resulting weld which is an alloy of the iron-base shim and the nickel-base alloy is crack-free.

mewcm 3:617:685

uuueu mates Patent [111 3, 7, 5

[72] Inventors Barry W. Brill-Edwards 3,094,414 6/1963 Franklin 75/ 1 71New York; 3,310,399 3/1967 Baldwin 75/171 Fereldoon Zahabl, Nynck, bothof N.Y. 3,391,033 7/1968 Chevigny et a1. 219/1 18 [21] Appl. No. 65,0633,398,256 7/1968 Foley 219/146 [22] Filed All:- 19, 1970 OTHERREFERENCES [45] Patented Nov.2, 1971.

H. f Assign chromauoy Americancorponuon Hokanson W l Kern Electron BeamWelding o Tungsten and Molybdenumf' Dec. 1961 (byHamilton-StanonngeburgN'y' dard) pages 15-30.

W. l. Kern; Electron Beam Welding of Bi-Metal Trubine [54] METHOD OFPRODUCING CRACKJREE Wheels June, 1962 (by Hamilton-Standard) pages 1- 4.

ELECTRON BEAM WELDS OF JET ENGINE Primary Examiner-J. V. TruheCOMPONENTS Assistant Examiner-O'Neill 8 Claims, 2 Drawing Figs.Attorney-Sandoe, Hopgood and Calimafde [52] 11.8. CI. 219/121 EB,

ABSTRACT: Crack-free welds of jet engine components [51] Ill!- Cl- 323.115/00 formed essentially of a heat resistant nickel base alloy having[50] Filld of Search 219/118Z a tendency to be weld crack sensitive areProduced y 121 14639504 abutting selected surface of at least a pair ofstructural ele- 75/17] ments of said nickel-base alloy, the elementsbeing assembled in welding relationship with an iron-base shimtherebetween,

[56] References Cited the elements being electron beam welded togetherinto a uni- UNITED STATES PATENTS tary structure by melting theiron-base shim at the interface of 5 3 K l tl 219/10 the abuttingsurfaces, whereby the resulting weld which is an 2,664,622 1954 Spitz29/366 alloy of the iron-base shim and the nickel-base alloy is crack-2,9ss,747 5/1961 Kutchera 2 19 11s [I equm M PATENTEDmva :sn I 3.617.685

INVENTORS' HARRY I. 80/ 150194003 BY PEPE/DOOM ZA HABI @IWXQZMQATTORNEY! blades, guide vanes, and the like, are generally made ofnickelbase alloys consisting essentially of substantial amounts ofchromium, molybdenum, tantalum, cobalt, titanium, aluminum and otherelements, which alloys are characterized by exhibiting high strength atelevated temperatures and of being highly hot corrosion and erosionresistant at temperatures'encountered in jet engines, for example, attemperaturesin the range of about 1,700 to 2,200 F. These alloys musthave relatively high-tensile strength at the operating temperatures,andexhibit, as well,-a highdegree of resistance to high-temperature creep.

in producing jet engine components from nickel-base superalloys, it isnot uncommon toweld together structural heatresistant elements intosu'bassemblies and then combine the welded subassemblies into largerstructural units. The Welding together of heat-resistant elements mayinclude, for example, the welding of an airfoil section to one or morebuttressesnh'e gang welding together of several guide vanesinto'subassemblies preparatory to mounting the-subassemblies into vaneshroud rings, and the welding of the structural elements which in useare subjected to high temperature corrosion and/or erosion. Anickel-base superalloy found to be particularly desirable and which hasrecently been introduced for the production of turbine blades, guidevanes,and the like, is one containing nominally about 8%Cr, about 10%Co, about 6% Mo, about 6% A1, about 4.3% Ta, about 1% Ti, about 0.015%B, about 0.08% Zr, with or without about ;l% to 1.5% l-lf, and thebalance essentially nickel. This is a gamma prime hardened alloy.Broadly speaking, the alloy-may range from about to 12% Cr, about 3% to8% Mo, about 2.3% to Ta, the combined Mo and Ta content ranging fromabout 5% to 14%, about 5% to 15.5% C0, up to about 7% Ti, up to about 8%Al, the combined Ti and Al content ranging from about 5% to 9%, up toabout 0.3% C, up to about 0.05% 8, up to about 1% Zr, up to about 2% Hi,up to about 2% Fe and the balance essentially nickel.

Preferred composition ranges found particularly useful include (A) about7.5% to 12% Cr, about 3% to 8% Mo, about 2.3% to 10% la, the combined Moand Ta content ranging from about 7% to 13%, about 5% to 10.5% C0, up toabout 2.5% Ti, about 5% to 7% Al, the combined Ti and Al content rangingfrom about 5.5% to 8%, up to about 0.2% C, up to about 0.05% B, up toabout 1% Zr,"up to about 2% l-lf, up to about 2% Fe and the balanceessentially nickel and (B) about 7.5% to 8.5% Cr, about 5.75% to 6.25%Mo, about 4% to 4.5% Ta, about 9.5% to 10.5% Co, about 0.8% to 1.2% Ti,about 5.75% to 6.25% Al, about 0.08% to 0.15% C, about 0.01% to 0.02% B,about 0.05% to 0.1% Zr, up to about 0.5% Fe, about 0.1% to 2% Hf and thebalance nickel.

in alloys of the aforementioned types, the presence of titanium,zirconium and aluminum, among others, is known to make such alloysweld-crack sensitive. This is particularly true under conditions ofwelding in which the weld is subjected to rapid cooling due to thenature of the weld, such as is characteristic of welds obtained byelectron beam welding.

It has recently been observed that this problem is even furtheraggravated when such alloys also contain hafnium in effective amounts,such as from about 0.1% to 2%, for example l to 1.5% or 2%.

The alloys referred to hereinabove and, in particular, composition (B)and the nominal composition are difficult to cast (e.g. investmentcasting of guide vanes) due to the tendency of such alloys to formshrinkage cracks on cooling from the molten phase. Such alloys as theforegoing exhibit a wide solidification temperature band and duringcooling are subject to cracking. Thus, extreme caution must be takenwhen producing structural elements or components for jet engines byinve'stment casting to assure a crack and shrinkage-free product.Because of the foregoing characteristics of the nickel-base alloysreferred to, structural elements of such alloys tend to crack, and, inmany instances, quite severely, at the weld when electron beam welded toform subassemblies. This is due to the fact that when the structuralelement is subjected to electron beam welding, the welding zone ischaracteristically narrow and cools rapidly due to the heat sinkpropensity of the substantially unheated base metal adjacent the weld.Since the alloy has a wide solidification temperature band, theexcessively high cooling rate at the weld leads to cracking transverseto the welding direction. This was particularly true in the case ofwelding second stage vanes into triplet assemblies (that'is, three'vanes electron beam welded together at their platform'faces) for usein recently designed high thrust jet engmes.

'Attm'pts'were made to overcome'this problem by inserting nickel-basealloy shims (0.002 to 0.020 inch thick) between the contact faces to bewelded on the theory that those nickel alloys'not subject to weldingcracks would avoid or prevent the'weld cracking of the base metal. Shimmaterials used and which were unsuccessful included nickel foil, lN-600(0.04% C, 1518% Cr, 7.2% Fe, 0.2% Mn, 0.2% Si and the balance nickel),l-lastelloy X (0.15% C, 22% Cr, 9% Mo, 20% Fe and the balance nickel),l'lastelloy W (24% Mo, 5% Cr, 5% Fe and the balance essentially Ni), andthe like. Other attempts to use nickel base shim material failed toovercome the problem.

ltis thus'the object of the invention to provide a method of electronbeam welding structural elements of a specified nickel-base alloy whileavoiding cracking at the weld.

Another object is to provide a method of electron beam welding jetengine components of a particular nickel-base alloy into a desiredassembly characterized by crack-free welds.

These and other objects will more clearly appear when taken inconjunction with the following disclosure and'the accompanying drawing,wherein:

P16. 1 shows two elements or members of a particular nickel-base alloyelectron beam welded without the use of a 'shim,'the weld beingcharacterized by'cracks transverse to the weld direction; and

FIG. 2 is a triplet assembly of three second stage vanes electron beamwelded at their platform faces as shown.

Stating it broadly, the invention is directed to method of producingcrack-free welds by electron beam welding of at least a pair ofheat-resistant structural elements consisting cssenti'ally of aheat-resistant nickel-base alloy containing by weight about 5% to 12%Cr, about 3% to 8% Mo, about 2.3% to 10% Ta, the combined Mo and Tacontent ranging from about 5% to 14%, about 5% to 15.5% C0, up to about7% Ti, up to about 8% Al, the combined Ti and Al content ranging fromabout 5% to 9%; up to about 0.3% C, up to about 0.05% B, up to about 1%Zr, up to about 2% Hf, up to about 2% Fe and the balance essentiallynickel. The method comprises providing at least one pair of structuralelements of the foregoing nickel-base alloy, assembling the elementswith selected surfaces thereof in abutting welding relationship with anironbase shim disposed between the abutting surfaces, and then electronbeam welding the elements into a unitary structure along theircontacting surfaces by the electron beam melting of the iron-base shimat the abutting surfaces of said elements, the resulting weld beingcrack-free and comprising an alloy of the nickel base structuralelements and the iron-base material.

It has been found that by employing an iron-base shim in producing theweld, that is, an iron-base material containing at least about 70% iron,more preferably at least about iron, and advantageously not exceedingabout 0.15% in carbon content, cracks are avoided in the resultingnarrow weld zone, despite the high cooling rate characteristic of weldsproduced by electron beam welding. Examples of iron-base materials areArmco iron (otherwise known as open hearth ingot iron containing 99.75%iron, some manganese, silicon, and less than 0.1% C), low carbon steelscontaining 0.05% to 0.15% C and the balance essentially iron, 304stainless steel (l8%20% Cr, 8%12% Ni, 0.08% C max, 1% Si max, 2% Mn maxand the balance iron), 410 stainless steel (1 1.5%-13.5% Cr, 0.5%140.15% C max, 1% Si max, 1% Mn max, and the balance iron). The carbon inthe iron-base material should be as low as is practicable and preferablynot exceed about 0.15% in order to minimize the formation of carbides atthe weld by reaction with carbide formers, such as Cr, Mo, Ti, Ta, etc.in the nickel-base alloy substrate. Excessive carbide formation cancause weld imbrittlement. As stated hereinbefore, we have found itadvantageous to use iron-base shims containing at least 95% iron andcarbon below 0.15% and, more preferably, not exceeding about 0.1%carbon. Examples of low carbon iron or steel containing at least about95% iron are as follows: SAE 1006 (0.08% C max), SAE 1008 (0.1% C max),SAE 1009 (0.15% C max), SAE 1010 (ODS-0.013% C), SAE 1012 (0.1 to 0.15%C) and the like. Steels containing at least 95% iron or even at least98% iron may contain optionally small amounts of other elements, such asMn, Si, Ni, Cr, etc. We have found it advantageous to use theaforementioned low carbon steels in preference to stainless steels inthat a wider range of welding parameters can be employed in producingcrack-free welds.

The invention is particularly applicable to the welding of alloys havingthe compositions (A) and (B) described hereinbefore and, in particular,the nominal composition comprising essentially about 8% Cr, about 10%Co, about 6% Mo, about 6% Al, about 4.3% Ta, about 1% Ti, about 0.015%B, about 0.08% Zr, about 1% to 1.5% Hf and the balance essentiallynickel.

As stated herein, attempts at using nickel-base shims of, for example,nickel foil or lN-600 alloy did not prevent weld cracking of theaforementioned nominal composition. Severe cracks were obtained when thesame alloy material was welded without a shim as shown in FEG. 1. Itmight be mentioned that welding of other nickel-base superalloys, suchas Udimet 700 (0.08% C, 15.0% Cr, 18.5% Co, 5.2% M0, 3.5% Ti, 4.3% A1,0.03% B and the balance nickel), under comparable conditions with orwithout a shim exhibited crack-free welds. It is thus apparent that thecracking phenomenon is characteristic of the alloys of the type referredto in FIG. 1.

However, when a cold-rolled steel shim containing 0.08 to 0.13% carbon,0.3 to 0.6% Mn, 0.04% max P, 0.05% max S and the balance iron was usedin welding the nominal com position, completely crack-free electron beamwelds were obtained. FIG. 2 is illustrative of three turbine vanes madeof the nominal composition containing about 1 to 1.5% Hf electron beamwelded at their contacted platform faces 11 and 12 into a tripletassembly using a low carbon steel shim. ln general, a steel shim atleast 2 mils (0.002 inch) in thickness will produce a satisfactorycrack-free weld. However, a 4 mil shim (0.004 inch) proved satisfactoryin producing the triplet assembly of F 16. 2. Adequate welds can beobtained with iron-base shims ranging in thickness from about 0.002 inchto about 0.01 inch. Cold-rolled steel shim stock is preferred in that(due to its stiffness) it can be readily handled in an assembly withoutmechanical deformation prior to welding.

Analysis of the weld (microprobe analysis) of the nominal nickel-basealloy produced from steel shim stock containing at least 98% Fe (alsosome Mn and Si) and less than 0.1% carbon, showed the followingcomposition by weight:

and the balance Co, Mo. Ta. Ti and residuals. For example, the dilutioneffect of using a low carbon steel shim in forming the desired weld withthe aforementioned nominal composition may result in a weld compositioncontaining about 7.4% Cr, 9.3% Co, 5.6% M0, 5.6% A1, 0.9% Ti, 3.7% Ta,7% Fe, about 1% Hf, and 59.5% Ni. When using a low carbon steel shimcontaining at least about 98% iron and the balance residuals, such asMn, Si, and other elements, the amount of iron in the crack-free weldmay range from about 5% to 10% by weight.

In welding the triplet shown in FIG. 2, the electron beam weldingparameters used in welding the aforementioned nominal composition usinga low carbon steel shim of the SAE 1010 type are as follows:

Voltage (kv. 22

Current (ma.) 50

Welding Speed Y Axis 54 ipm (inches per minute) Welding Speed X Axis 45i.p.m. (inches per minute) Focus 5.65 a.

Distance 6 inches Details as to electron beam welding are well known anddisclosed in various publications, such as in the Welding Journal, June1970 Edition, Welding Research Supplement, p. 259-8 to 266-S (Publishedby American Welding Society).

Thermal cycling of electron beam welds produced with the steel shimshowed good thermal fatigue strength. For example, no cracking wasinduced during 15 rapid air quench cycles from 1,600 F. to roomtemperature. It is not normal to consider using a steel shim in theelectron beam welding of nickelbase alloys of the type disclosed herein;the normal practice points towards using nickel-base shims. However,tests have shown that nickel-base shims do not prevent cracking ofelectron beam produced welds. To this extent, the results obtained withsteel shims are totally and surprisingly unexpected.

The invention is particularly applicable to the electron beam welding ofguide vanes of the type shown in FlG. 2, the guide vanes comprising anairfoil section 15 connected at each end to buttresses l3 and 14, thebuttresses being characterized by platform faces (adjacent welds 11 and12) by means of which the guide vanes are assembled together and thenelectron beam welded, low carbon steel shims being advantageously useddisposed between the abutting platform faces of the buttresses.

Although the present invention has been described in conjunction withpreferred embodiments, it is to be understood that modifications andvariations may be resorted to without departing from the spirit andscope of the invention as those skilled in the art will readilyunderstand. Such modifications and variations are considered to bewithin the purview and scope of the invention and the appended claims.

What is claimed is:

l. A method for producing a crack-free weld by the electron beam weldingof at least a pair of heat resistant structural elements consistingessentially of a heat-resistant nickel-base alloy containing by weightabout 5% to 12% Cr, about 3% to 8% Mo, about 2.3% to 10% Ta, thecombined Mo and Ta content ranging from about 5% to 14%, about 5% to15.5% C0, up to about 7% Ti, up to about 8% Al, the combined Ti and Alcontent ranging from about 5% to 9%, up to about 0.3% C, up to about0.05% B, up to about 1% Zr, up to about 2% Hf, up to about 2% Fe and thebalance essentially nickel which comprises,

providing said at least one pair of structural elements of saidnickel-base alloy,

assembling said elements with selected surfaces thereof in abuttingwelding relationship with a low carbon iron-base shim disposed betweensaid abutting surfaces,

and then electron beam welding said elements into a unitary structure bythe electron beam melting of the iron-base shim at the abutting surfacesof said elements,

whereby a narrow crack-free weld is obtained formed as an alloy of saidnickel-base alloy with said iron-base shim elements.

2. The method of claim 1, wherein the nickel-base alloy of thestructural elements being welded is selected from the group consistingof by weight.(A) about 7.5% to 12% Cr, about 3% to 8% Mo, about 1.3% toTa, the combined Mo and Ta content ranging from about 7% to 13%, about5% to 10.5% C0, up to about 2.5% Ti, about 5% to 7% Al, the combined Tiand Al content ranging from about 5.5% to 8%, up to about 0.2% C, up toabout 0.05% B, up to about 1% Zr, up to about 2% Hf, up to about 2% Feand the balance essentially Ni; and (B) about 7.5% to 8.5% Cr, about5.75% to 6.25% Mo, about 4% to 4.5% Ta, about 9.5% to 10.5% C0, about0.8% to 1.2% Ti, about 5.75% to 6.25% Al, about 0.08% to 0.15% C, about0.01% to 0.02% B, about 0.05% to 0.1% Zr, up to about 0.5% Fe, about0.1% to 2% Hf, and the balance essentially nickel.

3. The method of claim 1, wherein the iron-base shim is a steelcontaining at least about 95% iron.

4. The method of claim 2, wherein the nickel-base alloy comprises about8% Cr, about 6% Mo, about 4.3% Ta, about 10% Co, about 6% Al about 1%Ti, about 0.015% B, about 0.08% Zr, about 1% to 1.5% l-lf and thebalance essentially nickel.

5. A method for producing a crack-free weld by the electron beam weldingof at least a pair of heat resistant jet engine guide vanescharacterized by an airfoil section connected via their ends tobuttresses having platform faces by means of which one guide vane can bewelded to the other, the guide vanes consisting essentially of a heatresistant nickel-base alloy containing by weight about 5% to 12% Cr,about 3% to 8% Mo, about 2.3% to 10% Ta, the combined Mo and Ta contentranging from about 5% to 14%, about 5% to 15.5% C0, up to about 7% Ti,up to about 8% Al the combined Ti and Al content ranging from about 5%to 9%, up to about 0.3% C, up to about 0.05% B, up to about 1% Zr,'up toabout 2% Hf, up to about 2% Fe and the balance essentially nickel whichcomprises,

providing said at least one pair of said guide vanes of said nickel-basealloy,

assembling said guide vanes with selected platform faces thereof inabutting welding relationship with and ironbase shim disposed betweensaid abutting surfaces,

and then electron beam welding said elements into a unitary structure bythe electron beam melting of the iron-base shim at the abutting faces ofsaid buttresses,

whereby a narrow crack-free weld is obtained formed as an alloy of saidnickel-base alloy with said iron-base shim.

6. The method of claim 5, wherein the nickel-base alloy of thestructural elements being welded is selected from the group consistingof by weight (A) about 7.5% to 12% Cr, about 3% to 8% Mo, about 2.3% to10% Ta, the combined Mo and Ta content ranging from about 7% to 13%,about 5% to 10.5% C0, up to about 2.5% Ti, about 5% to 7% Al thecombined Ti and Al content ranging from about 5 .5 to 8%, up to about0.2% C, up to about 0.05% B, up to about 1% Zr, up to about 2% Hf, up toabout 2% Fe and the balance essentially Ni; and (B) about 7.5% to 8.5%Cr, about 5.75% to 6.25% Mo, about 4% to 4.5% Ta, about 9.5% to 10.5%C0, about 0.8% to 1.2% Ti, about 5.75% to 6.25% Al about 0.08% to 0.15%C, about 0.01% to 0.02% B, about 0.05% to 0.1% Zr, up to about 0.5% Fe,about 0.1% to 2% Hf, and the balance essentially nickel.

7. The method of claim 5, wherein the iron-base shim is a steelcontaining at least about iron.

8. The method of claim 6, wherein the nickel-base alloy comprises about8% Cr, about 6% Mo, about 4.3% Ta, about 10% Co, about 6% Al about 1%Ti, about 0.015% B, about 0.08% Zr, about 1% to 1.5% Hf and the balanceessentially nickel.

a t a a a

1. A method for producing a crack-free weld by the electron beam weldingof at least a pair of heat resistant structural elements consistingessentially of a heat-resistant nickel-base alloy containing by weightabout 5% to 12% Cr, about 3% to 8% Mo, about 2.3% to 10% Ta, thecombined Mo and Ta content ranging from about 5% to 14%, about 5% to15.5% Co, up to about 7% Ti, up to about 8% Al, the combined Ti and Alcontent ranging from about 5% to 9%, up to about 0.3% C, up to about0.05% B, up to about 1% Zr, up to about 2% Hf, up to about 2% Fe and thebalance essentially nickel which comprises, providing said at least onepair of structural elements of said nickel-base alloy, assembling saidelements with selected surfaces thereof in abutting welding relationshipwith a low carbon iron-base shim disposed between said abuttingsurfaces, and then electron beam welding said elements into a unitarystructure by the electron beam melting of the iron-base shim at theabutting surfaces of said elements, whereby a narrow crack-free weld isobtained formed as an alloy of said nickel-base alloy with saidiron-base shim elements.
 2. The method of claim 1, wherein thenickel-base alloy of the structural elements being welded is selectedfrom the group consisting of by weight (A) about 7.5% to 12% Cr, about3% to 8% Mo, about 1.3% to 10% Ta, the combined Mo and Ta contentranging from about 7% to 13%, about 5% to 10.5% Co, up to about 2.5% Ti,about 5% to 7% Al, the combined Ti and Al content ranging from about5.5% to 8%, up to about 0.2% C, up to about 0.05% B, up to about 1% Zr,up to about 2% Hf, up to about 2% Fe and the balance essentially Ni; and(B) about 7.5% to 8.5% Cr, about 5.75% to 6.25% Mo, about 4% to 4.5% Ta,about 9.5% to 10.5% Co, about 0.8% to 1.2% Ti, about 5.75% to 6.25% Al,about 0.08% to 0.15% C, about 0.01% to 0.02% B, about 0.05% to 0.1% Zr,up to about 0.5% Fe, about 0.1% to 2% Hf, and the balance essentiallynickel.
 3. The method of claim 1, wherein the iron-base shim is a steelcontaining at least about 95% iron.
 4. The method of claim 2, whereinthe nickel-base alloy comprises about 8% Cr, about 6% Mo, about 4.3% Ta,about 10% Co, about 6% Al about 1% Ti, about 0.015% B, about 0.08% Zr,about 1% to 1.5% Hf and the balance essentially nickel.
 5. A method forproducing a crack-free weld by the electron beam welding of at least apair of heat resistant jet engine guide vanes characterized by anairfoil section connected via their ends to buttresses having platformfaces by means of which one guide vane can be welded to the other, theguide vanes consisting essentially of a heat resistant nickel-base alloycontaining by weight about 5% to 12% Cr, about 3% to 8% Mo, about 2.3%to 10% Ta, the combined Mo and Ta content ranging from about 5% to 14%,about 5% to 15.5% Co, up to about 7% Ti, up to about 8% Al the combinedTi and Al content ranging from about 5% to 9%, up to about 0.3% C, up toabout 0.05% B, up to about 1% Zr, up to about 2% Hf, up to about 2% Feand the balance essentially nickel which comprises, providing said atleast one pair of said guide vanes of said nickel-base alloy, assemblingsaid guide vanes with selected platform faces thereof in abuttingwelding relationship with and iron-base shim disposed between saidabutting surfaces, and then electron beam welding said elements into aunitary structure by the electron beam melting of the iron-base shim atthe abutting faces of said buttresses, whereby a narrow crack-free weldis obtained formed as an alloy of said nickel-base alloy with saidiron-base shim.
 6. The method of claim 5, wherein the nickel-base alloyof the structural elements being welded is selected from the groupconsisting of by weight (A) about 7.5% to 12% Cr, about 3% to 8% Mo,about 2.3% to 10% Ta, the combined Mo and Ta content ranging from about7% to 13%, about 5% to 10.5% Co, up to about 2.5% Ti, about 5% to 7% Althe combined Ti and Al content ranging from about 5.5% to 8%, up toabout 0.2% C, up to about 0.05% B, up to about 1% Zr, up to about 2% Hf,up to about 2% Fe and the balance essentially Ni; and (B) about 7.5% to8.5% Cr, about 5.75% to 6.25% Mo, about 4% to 4.5% Ta, about 9.5% to10.5% Co, about 0.8% to 1.2% Ti, about 5.75% to 6.25% Al about 0.08% to0.15% C, about 0.01% to 0.02% B, about 0.05% to 0.1% Zr, up to about0.5% Fe, about 0.1% to 2% Hf, and the balance essentially nickel.
 7. Themethod of claim 5, wherein the iron-base shim is a steel containing atleast about 95% iron.
 8. The method of claim 6, wherein the nickel-basealloy comprises about 8% Cr, about 6% Mo, about 4.3% Ta, about 10% Co,about 6% Al about 1% Ti, about 0.015% B, about 0.08% Zr, about 1% to1.5% Hf and the balance essentially nickel.